The Marvel Comicsuniverse hosts a number of demons, many of whom are at times at conflict with gods and angels. All possess varying degrees of mystical power, feed upon souls for self-sustenance, and are inclined towards dark or “black” magic - evil.

During the era in which the first single-celled organism formed on Earth, Demiurge achieved consciousness after being formed and coalesced from the Earth's biosphere. As conditions on Earth began to support life, it became aware, and wanting to know itself, the Demiurge split itself into countless aspects, each of which wanted consciousness and to manifest into new entities. These entities later become known as the "Elder Gods".

However, certain demons, such as Lucifer, Kazann, and Asmodeus, have other origins, such as originally being angels having fallen from Heaven after a massive failed insurrection against the Judeo-Christian God long before the dawn of humanity, or hailing from other mystical dimensions adjacent to Earth.

The Elder Gods are the forerunners to the modern gods and Demons of Earth.

Chthon began devoting itself to the study and manipulation of mystical energies, becoming Earth's first master of black magic.[1]

Gaea came into being and was the “Protector of the Emerging Life” that began in the Seas.

Set, the “God of the Dead” spawned a number of offspring (e.g. “Sligguth” and “Damballah”).

Oshtur was the goddess of the stars and left Earth early on before the fall of the Elder Gods. She mothered Agamotto, the first Sorcerer Supreme; she is the third member of the mystical Vishanti.

Realizing he could increase his own power by consuming the essence of his fellow Elder Gods, Set became the first being on Earth to murder another. By consuming the life energies of a fellow Elder God, Set started down the path of degeneracy. Other Elder Gods quickly began following Set's example, killing each other to gain more power. The more they consumed, the more they hungered for power, becoming insatiable.

Many became corrupt and began warring to satisfy the thirst for power, the victor feeding off the others. After millions of years, all the Elders except for Gaea had degenerated to less than their Godhood, becoming demonic in nature.

Gaea, fearing the Elders' war with each other would destroy the evolving life on the planet, mated with a reincarnation of the Demiurge and gave birth to Atum, who became dedicated to eradicating his Forefathers.

Foreseeing the threat Atum was to his existence, Chthon inscribed all the mystical knowledge he had learned through millennia of evil onto a parchment to be his touchstone within the Earth dimension, the Darkhold.

Atum indeed became a threat to the Elder Gods, as he began destroying them for their evil and degradation, absorbing their energies into himself. The energies he absorbed caused him to undergo a metamorphosis into the form of “Demogorge,” the God-Eater.

Many of the Elders fell to Atum and those who weren't destroyed, fled to other dimensions:

Chthon, sensing the end was near, cast a spell that allowed him an escape into another dimension before the Demogorge could slay him. Before he left, Chthon left the parchment containing his mystical knowledge in this dimension.

Set, witnessing what Chthon had done, replicated the spell allowing him and his offspring to escape. Gaea was the only original Elder God permitted to exist on the planet, and she infused her godly essence into the Earth and into all living things - ultimately becoming “Mother Earth”.

The Demogorge released the energies he had absorbed, reverting to the form of Atum. He then took residence within Earth's Sun.

Over millennia, the energies that Demogorge had released when he reverted into Atum eventually manifested into a number of different beings:

(Note: Whether Atum fathered the original founders/creators of Earth’s pantheons is speculative, as is whether or not Atum is the creator of Earth's pantheons. Similarly, Gaea was said to be the mother of “Ouranus.”)

Nun

Ouranus

Buri, Father to a number of different pantheons of “New Gods.”

NOTE: It has been implied that the demonic energies released by the Demogorge after destroying most of the degenerated Elder Gods coalesced and gave rise to demons such as Mephisto, Satannish, Thog, Marduk Kurios, etc.

To fuel his own power, the Elder God Set, from his pocket dimension, began drawing psychic energy from the dinosaurs, the dominant life forms of Earth. Eventually Set's continued feeding on the dinosaurs helped bring about significant drops in their population.

Gaea knew the dinosaurs were at an evolutionary dead end and allowed Set to continue his feeding knowing that he was quickly depleting his main supply of energy. Set, aware that Gaea was allowing the extinction of the dinosaurs, became infuriated and commanded the dinosaurs to seek out and kill all mammals (which Gaea had selected as Earth’s dominant species over the dinosaurs).

Gaea sensed Set's command over the dinosaurs and summoned the Elder God. Set appeared on Earth in physical form for the first time as a giant serpent, and attacked Gaea. She summoned her son Atum to protect her. Atum (in his form of Demogorge) engaged Set in battle and destroyed his head. However, Set was not killed and two heads grew back. Set and Atum battled for decades. Many disasters befell the Earth during this time, some caused by the titanic struggle (which brought about the extinction of the dinosaurs in the Marvel Universe).

The mammals were sheltered from the devastation by Gaea. Eventually Set, drained of power, was forced to withdraw from the Earth dimension. By this time, Set had grown seven heads to replace the ones destroyed in battle. With his power all but exhausted, Set could no longer journey to the Earth dimension without aid. Demogorge reverted to Atum and returned to his dwelling place in the sun.

Their origins are shrouded in mystery - a few are fallen angels or gods who fell out of favor with their pantheon, whereas some are the descendants of degenerate Elder Gods and others were shaped by the subconscious desires of their earliest worshippers.

This category also includes messengers and servants who work for these “Rulers of Hell”; "lesser demons" that share the same origins as their masters, but are usually less powerful (although still superior to most mortals).

Hell is broken into several smaller kingdoms ruled over by entities generally at odds with each other. Most of these entities are devils and those considered powerful enough to stand against the strongest rulers in Hell are referred as the Hell-lords. Those to either have carried this distinction at some point or presently bear this identification are:

Some demons seem to be entirely unrelated to earth and humanity's past - these creatures are often non-humanoid in form and utterly alien in motivation. They are referred to as Class Three Demons in Marvel's Official Handbook.

Several extra-dimensionalmystical beings exist in the Marvel Universe (that do not fall into any of the three preceding categories). They are powerful and evil enough to be considered demons. Beings of this sort include evil mortal beings that have attained great power, as well as beings that have been referred to as demons but whose origins have yet to be definitively defined or revealed. They include:

The Octessence is made up of eight powerful principalities (Balthakk, Cyttorak, Farallah, Ikonn, Krakkan, Raggadorr, Valtorr, Watoomb), a number of whom are routinely invoked for the power of spells related to their particular area of magical knowledge. Roughly a thousand years ago, they disagreed on which of them was most powerful. To settle the question they entered into the Wager of the Octessence. Each placed a small fraction of its magical might into a token, and then established a temple on Earth to house it. The first human to find and touch the artifact would gain the power and lose his will to the artifact's master, becoming an Exemplar: a creature of focused magical might. When all eight Exemplars appeared, they would perform the Ceremony of the Octessence, the construction of a great magical engine to enslave the will of humanity. Then the Examplars would divide the world into eighths, and each would battle the others (using his own powers and armies made of his enslaved eighth of the population) until only one remained. The first artifact uncovered was the Crimson Ruby of Cyttorak, which empowered The Juggernaut. Only years later would the other Exemplars appear.

Balthakk first appeared in X-Men #12 (1965). While meeting to establish the terms of the Wager, it appeared as little more than a free-floating cloud of energy or charged particles. It empowered the Blinding Brazier of Balthakk and through it the Exemplar called Inferno.

Cyttorak first appeared in Dr. Strange (vol. 3) #44, published in 1992 - nearly 30 years after its first mention in 1964 (Strange Tales (vol. 1) #124). While meeting to establish the terms of the Wager, it appeared as a semblance of Juggernaut but completely covered in armor. It has involved itself in human activities more than other members of the Octessence, perhaps owing to the early discovery of the Ruby of Cyttorak (referred to as the Crimson Crystal of Cyttorak in the Wager storyline, possibly to avoid confusion with the Ringed Ruby of Raggadorr). Cytorrak's gem lent enormous strength and durability to Cain Marko, transforming him into Juggernaut. It would be years before Marko's purpose as an Exemplar became known, when the other Exemplars appeared. Marko's betrayal of the other Exemplars contributed to their eventual defeat.

Farallah first appeared in Iron Man (vol. 3) #22. While meeting to establish the terms of the Wager, it appeared as a powerful humanoid with ruminant characteristics: short, coarse, dark fur and spiral horns close to the head like those of certain sheep. A large hump similar to that of a dromedary adorned its back, and its hands ended in very sharp nails or claws. It empowered the Fearsome Fist of Farallah, which granted feral combat skills and superhuman speed and coordination to the Exemplar called Carnivore.

Ikonn first appeared in Dr. Strange (vol. 2) #47 (June 1981) and is the creation of Roger Stern and Gene Colan. It is a powerful mystical entity that Doctor Strange and other sorcerers regularly invoke, most often to produce a powerful spell of illusion-crafting called "The Images of Ikonn." Ikonn can create extremely believable illusions and has been titled the "Lord of Illusions." It can disrupt reality, and if it gains control over a world it can make its illusions real. Meeting to establish the terms of the Wager, it appeared as a greyish insectoid/humanoid adorned with dark greenish spikes and pupil-less grey-green eyes. Each limb ended in four radially arranged claws. It had a proboscis where the mouth would normally be. As with any being so powerful, and especially one versed in illusion, one can only speculate as to Ikonn's real form. For the Wager, it invested power into the Ivory Idol of Ikonn, a token that granted Olisa Kabaki powerful telepathic and mind control abilities as the Exemplar Bedlam.

Krakkan first appeared in Iron Man (vol. 3) #22 during the meeting to decide the terms of the Wager, appearing there as a grey armored figure; this armor possessed a number of long and very sharp blades. It crafted the Kestrel Key of Krakkan. In Thor (vol. 2) #17, Bridget Malone found this key and became the Exemplar called Conquest, the "living embodiment of battle."

Raggadorr first appeared in Iron Man (vol. 3) #22 (1999). While meeting to establish the terms of the Wager, it appeared as a creature with a four-armed but otherwise humanoid torso, and a blue-colored serpentine lower body. Its face remained concealed behind a heavy blue helm from which projected bluish horns similar to those of a ram. Powerful magicians invoke Raggadorr's name to empower certain of their magical spells, most commonly The Rings of Raggadorr. It empowered the Ringed Ruby of Raggadorr and through it the Exemplar called Stonecutter.

Valtorr appeared at the Wager meeting in the form of a greyish, possibly armored snake possessing a crest of slightly raised overlapping plates or scales. Magicians invoke Valtorr in spells to command vapors and gasses. The Vapors of Valtorr create what amounts to a gaseous extension of the magician's will; these vapors have properties the magician imparts to them during the casting. The Verdant Vial of Valtorr transformed Stark-Fujikawa employee Yoshiro Hashiman into Decay, an Exemplar with the power to corrupt and destroy with his touch.

Watoomb presented itself as an armored humanoid (or possibly a creature bearing natural armor) with aspects both feline and insectoid, in various shades of yellow, orange, and brown. A signature spell is the Winds of Watoomb, which can carry a caster across light-years of space, and can even pierce dimensional barriers. Watoomb crafted the Wicked Wand of Watoomb, roughly 30 cm from tip to tip. The ends of this device are carved with the visages of demons. This device granted Nicolette Giroux with a portion of Watoomb's power and will, creating Tempest; Dr. Stephen Strange had possessed the device for years prior to this event without transforming into an Exemplar.

The Six-Fingered Hand was a group of six lesser demons acting as pawns of more powerful demons, including Mephisto. The legion of demons once plotted to merge Earth and Hell, but the Defenders successfully opposed their plan. The six are also responsible for the creation of the Lesser Grey God, a statuette that has the power to reactivate old curses.

This loose collection of various demons (but also wizards and sorcerers) was made up of rulers of the various realms of the nether world (most prominently Mephisto, Dormammu, Umar, Nightmare, Surtur, Thog, and Pluto). While normally separated from and opposed to each other they formed a tenuous alliance against the Archenemy at the request of Magik (Amanda Sefton), then ruler of Limbo.

The Devil's Advocacy is a location in the neutral realm where the Demons and their affiliations discuss matters of importance at the empty throne of Satan which nobody was up to taking the name or mantle. It is a counterpart of the Infinite Embassy (which was created by Living Tribunal as a meeting place of the different Gods) The Devil's Advocacy first appeared in the Fear Itself storyline where the Demons and their affiliations (including but not limited to Adversary, Asmodeus, Asmodiar, Asteroth, Avarrish, Big Mother, Blackheart, "Brood Satan," Chaos, Chthon, Cyttorak, D'Spayre, Dagon, Daboia, Damballah, Darklove, Demogorge, the Demons of Muspelheim, Dormammu, Kazann, Malonch, Marduk Kurios, Natohk's Emissary, Olivier, Pythias, Satannish, Shuma-Gorath, Sligguth, and Stonecold) meet to discuss the impact of the rise of the Serpent and what this will mean to them. Cyttorak mentions that the Serpent stole Juggernaut from him, Dormammu remained silent, the Demons of Muspelheim didn't speak of Surtur's impending release, and Marduk Kurios mocked Mephisto who tolerated it as he was fond of his children. The rest of the meeting was long and did not achieve a united resolution for the threat of the Serpent.[4]